1. Field of the Invention
The invention concerns apparatus for the wireless transmission of a control signal to the control path of a controlled semiconductor valve.
2. Description of the Prior Art
In a known apparatus of the above-type, at the transmitter location of the apparatus, the control signal and a carrier frequency are fed to a modulator which develops a frequency-modulated output signal. A transmitting antenna, coupled to the modulator output, then radiates the frequency modulated output signal via a radio wave which propagates over a radio transmission path. Along the transmission path, at the receiver location of the apparatus, a receiver antenna receives the propagating frequency modulated signal and couples it to a demodulator. The demodulated output is then conveyed to the control path of the semiconductor controllable valve for exercising control thereover.
Also located at the receiver location of the apparatus is an indicating means for developing a signal indicative of the state of the controllable valve. This indicating means comprises an indicating transmitter and a modulator and its output signal is coupled to the receiver antenna and retransmitted as a back reporting or remote-indication signal.
The aforesaid remote-indication signal, once propagated, passes back over the transmission path and is received by the transmitter antenna. From the latter, it is coupled into a modulation dependent signal filter which is arranged between the transmitter antenna and the transmitter modulator. The filter output, in turn, is cupled to a remote indication receiver which separates therefrom the information therein indicative of the state of the controlled valve.
It is an object of the present invention to provide a modulation-dependent signal filter for the above-described apparatus which can be readily manufactured and which provides good signal selectivity.